1. Field of the Disclosure
The present disclosure relates to a nano particle used as an illuminator in an electronic device, and more particularly, to a nano particle coated with a material having a lower index of refraction than that of the nano particle on the surface of the nano particle, for improving the luminous efficiency of the electronic device.
2. Description of the Related Art
Recently, many attempts have been made to employ a nano particle as an illuminator of an electronic device. Among the nano particles, a quantum dot (QD) as a compound semiconductor nano particle is being actively investigated.
The quantum dot is a semiconductor material having a nano size, and shows a quantum confinement effect. The quantum dot receives light from an excitation source, and if it reaches an energy excitation state, it emits energy as much as the energy band gap of the quantum dot. Thus, when the size of the quantum dot or the composition of the quantum dot is controlled, the corresponding energy band gap can be controlled so as to emit light having various wavelengths. Therefore, the quantum dot can be used as an illuminator of an electronic device.
U.S. Pat. No. 6,501,091 discloses a light emitting diode in which a quantum dot is scattered in a matrix and is used as an illuminator. In order to fabricate a light emitting diode, U.S. Pat. No. 6,501,091 discloses a method of forming polymer having dispersed quantum dots by mixing a replaced organic ligand, a monomer having a good affinity, and a small amount of catalyst with quantum dots coating the surface of the quantum dots, and applying heat.
FIG. 1 illustrates a process in which an illuminator absorbs the light from a light source, and emits light to the outside.
The light transmitted through a matrix is partially reflected S2 at the interface between a nano particle and the matrix, and a remainder of the light is absorbed by the nano particle as an illuminator. The absorbed light changes the energy state of the nano particle to an excitation state, and changed light is emitted (Lout). When the light emitted from the nano particle is reflected due to the difference of indexes of refraction between the nano particle and the matrix, it may be reabsorbed by the illuminator and the luminous efficiency is decreased. That is, since light scattering occurs at the interface between the matrix and the illuminator due to the difference between an index of refraction of the matrix Nm and an index of refraction of the illuminator Np, the absorption efficiency of the optical energy is deteriorated, and the light emitted from the illuminator is reflected from the interface between the matrix and the illuminator, and is reabsorbed by the illuminator, thereby decreasing the luminous efficiency.